In normal X-ray imaging, radiography is executed by a film screen system or an IP (Imaging Plate) system using photostimulable phosphor. It takes several minutes to see a sensed image. This is because a time is necessary for a film process in the former system and for reading by a reading apparatus in the latter system.
The radiographed state, i.e., whether exposure in radiography was appropriate or whether the target was radiographed at an accurate angle is confirmed after such a wait time. For this reason, if radiography fails, the workflow of X-ray inspection may be disturbed.
When the radiography result can be confirmed at an earlier timing, it can early be determined whether re-imaging is necessary, and a satisfactory workflow of X-ray inspection can be maintained.
From this viewpoint, for example, Japanese Patent Laid-Open No. 2002-186606 discloses an X-ray diagnosis apparatus operation method which executes various kinds of correction for data obtained by undersampling a whole image and then displays the data by using a solid-state detector for X-ray image display.
In this X-ray diagnosis apparatus operation method, whole image data is acquired from the detector. Then, a low-resolution image (reduced image) is generated by undersampling the data and previewed on the basis of this data. To do this, data transfer from the detector to the operation unit must be done for all image data.
The pixel matrix of a general digital X-ray imaging apparatus includes several thousand x several thousand pixels (e.g., 2,000×2,000 pixels or more). Since data per pixel is 8 to 16 bits, an enormous data amount must be transferred. To shorten the time until preview display under these circumstances, the data transfer rate must be increased by using a multi-bit data transfer path or increasing the data transmission rate.
However, in the former case, the cable of the data transfer path becomes thick, resulting in poor portability. In the latter case, the cost of parts of I/O units increases, and high transmission quality can hardly be ensured.
Image data cannot be used as a diagnostic image until it undergoes preprocesses such as offset correction, gain correction, and defect correction and post-processes such as dynamic range adjustment and display LUT adjustment.
In the post-processes, parameters for image adjustment change depending on the type (e.g., target part) of a sensed image. To automatically adjust the quality of the diagnostic image, the parameters for the post-processes must be determined by analyzing the sensed image. When a preview image can be used for this analysis, the processing speed of the system can be increased. For this purpose, however, a high-quality preview image is necessary. The image quality is insufficient in an uncorrected coarse image or a simple offset correction image using dummy offset data obtained by pre-calibration.
The characteristics of the parts of the imaging unit change depending on the environment such as ambient temperature. Dark noise in the X-ray detector in the imaging unit varies even depending on the radiographic operation time. Calibration data cannot contain these variation components before radiography. To minimize the variation components, offset data must be acquired by reproducing the same operation as in radiography in an X-ray non-irradiation state immediately after radiography.
However, even with this measure, when a reduced image is generated by undersampling after all pixel data are transferred, the time required for data transfer is a bottleneck, resulting in a problem in shortening the time until image display.